The Role of Soil Carbon Sequestration as a Climate Change Mitigation Strategy: An Australian Case Study
Round 1
Reviewer 1 Report
Review of the manuscript ’Where do we stand in respect to soil carbon farming as a climate change mitigation strategy?’ Manuscript ID: soilsystems-1681278
General comments
The author has submitted a manuscript to a review with the aim to give the reader up-to-date information about the situation with C sequestration in soil called ‘farming of soil C’.
The review is subdivided into the three main sections (plus Conclusions)
# ‘Practical implications of a soil carbon negative-emission strategy with the two subsections ‘Additionality and leakage’ and ‘Permanence and risk of reversal’
# ‘The potential for increasing soil C sequestration, with one subsection ‘Projections for the Australian landscape’.
# ‘Field measurements of soil carbon sequestration’ with the seven subsections ‘Technical and financial considerations’, ‘Examples of field measurements of SCS in Australia’, ‘Monitoring, reporting and verification (MRV)’, ‘Costs and benefits of a soil C project’, ‘Co-benefits’, ‘Abatements of national emissions’, and ‘Financial outcomes’
The review covers cropland and pastures and gives a good spectrum of socio-economic aspects as well as considerations on projects vs funding. The author also gives an overview with focus on recommendations by IPCC, CSIRO and other organizations as well as on different projects and considerations about policy. There is also a section for results for actual measurements, which shows actual and expected amounts of sequestered C.
The review is well written and made an interesting reading. Further, it is one of several much needed overviews that give new starting points for research. Still, it has a complete focus on Australian conditions. I am of the opinion that the review could be published, let be that the author should consider a few points, mainly # 1 (below). Still, if this ms fits in Soil Systems or not depends on the journal’s policy and that is up to the editor to decide.
Specific comments
# 1. Although the ms is well written and interesting to read it gives me the impression of a report, which rather belongs among government agencies and has been transformed into an ms. A borderline between such a report and a scientific paper is not always clear. Still as a personal opinion – I miss critical comments to the project outlines and their limits that have been decided or approved of by e.g. IPCC and ERF. There is no comment about the different meanings of ‘stability’ of the soil C and the different time periods that C is considered stable or sequestered, e.g. 100 years as recommended by UNFCCC (lines 136 and 137) and 2 years in lines 125 to 126. At least there should be comments and ideally some evaluation about that as the stability and duration of C sequestration is a basic for meaningful research.
The author has focused on sequestration to a depth of 30 cm and refers to recommendations from IPCC. I do not argue about a general recommendation, but it may be of interest to the reader to have information a bit outside of the recommendation. Do we know what happens in the first 10 cm and the depth below 30 cm? Is the recommendation itself above criticism?
# 2. The ms title covers mainly the topic – still it may give the reader an impression of a global view. Not until line 65 did I have a confirmation that the author presents a case study. If the author adds ‘A Australian case study’ to the title the reader will be better informed about what to expect.
# 3. The number of acronyms and abbreviations is high – I counted 13 - and personally I find that it disturbs my reading to go back and search for their meanings. I expect that an international readership has the same problem. I can see two ways of approaching this problem, one being a short table and the other to simply cut back on the number of acronyms used, possibly a combination.
# 4. The division into subsections is not very clear to me and that may be emphasized by the lack of difference in setting between the 1st and the 2nd levels. An example is the main section The potential for increasing soil C sequestration, with the only subsection ‘Projections for the Australian landscape, where the 1st and 2nd levels have the same design. Further, do all the subsections to ‘Field measurements of soil carbon sequestration’’ really belong under that main title? The subsections Costs and benefits of a soil C project, ‘Co-benefits’, ‘Abatements of national emissions’, and ‘Financial outcomes’ seem to me rather to belong under another headline.
# 5. The author has used ‘Soil carbon farming’ in the title of his ms. To me ‘farming’ gives the idea of a general cultivation of edible plants. Still the term ‘Soil carbon farming’ could mean the work to sequester soil carbon also in forest systems.
A detail
In line 319 there is a repetition of ‘of the of the’.
Author Response
Please see the submitted attached file
Author Response File: 
Author Response.pdf
Reviewer 2 Report
I read this manuscript carefully, but it failed to impress me. The description seems comprehensive, but there is not clear point of view. It is more like a work report. It also fails to give a clear answer to the question raised by the title.
It is hard for me to give a specific comments. The content of the manuscriptis very much, but the internal logic between the contents of the paper is
very loose. For examples, “If this, lines 37-39, is a topic sentence, the rest
of the sentence should be about that topic. However, the rest of the content
did not revolve around this theme. Moreover, it is not appropriate to conclude
an article with other people's opinions (references appeared in the conclusion).
It is very important to draw a clear view of the study for an article.
Author Response
Please see the attached file
Author Response File: Author Response.pdf
Reviewer 3 Report
GENERAL COMMENTS
Soil organic matter plays an important role influencing soil functions and the global carbon cycle. It determines the nutrient cycle when it is decomposed and can also withdraw carbon from the atmosphere and sequester it in the soil for long periods. It is estimated that SOM stores two to three times as much C as the atmosphere. Different soil management practices strongly affect SOC stocks and appropriate soil management has the potential to improve nutrient availability and C sequestration. The submitted article “Where Do We Stand in Respect of Soil Carbon Farming as a Climate Change Mitigation Strategy?” is very interesting because it shows an example of the valorisation of carbon stocks in Australia, an initiative of particular interest in a context where the agricultural sector and soil play an essential role in the mitigation and adaptation to climate change.
SPECIFIC COMMENTS
Introduction
Line 30- In addition to 4 per thousand, have emerged different initiatives at the international level (Adapting African Agriculture - AAA, Platform on Climate Action in Americas - PLACA, Living Soils of the Americas - LiSAM… among others), under which the soil has been highlighted as carbon sink.
Line 37-38 “Various schemes have been developed around the world whereby land managers are encouraged to implement practices to draw down CO2 from the atmosphere and store 38 it in soil organic matter (SOM), described as a negative emissions strategy.” Please provide references
Line 43-44 “normally 0.3 m as recommended by the International Panel for Climate Change (IPCC)” Please provide reference. Other institutions such as FAO suggest other depths. It would be interesting to show these differences in this section.
Line 58 “soil C farming” A definition of this concept is necessary
A more complete introduction is required in which the state of the art and possible trends are explored in more depth.
Additionality and leakage
Line 82 In addition, with increasing soil organic carbon, soil aggregates and mineral surfaces become less effective in protecting the SOC from microbial activity, thus limiting the soil's ability to accumulate C (i.e. saturation).
Line 123 “CEA” please define the acronym
Projections for the Australian landscape
Line 160 More references should be included
Monitoring, reporting and verification (MRV)
who is responsible of soil monitoring?
Line 306 “which a report must be submitted to the CER” What should the report include? What aspects must it cover?
Co-benefits
This section could be improved by including more references that discuss the benefits of increased levels of soil carbon sequestration through the implementation of sustainable management practices.
Conclusions - a take-home message
This section could be rewritten to be more concise and to show the conclusions reached by the author regarding Australian government's long-term emissions reduction plan.
As a formal aspect, it would be important to include a section and sub-section numbering to facilitate the easy legibility of the document.
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments for author File: 
Comments.docx
Author Response
Responses in the reviewer's report in italics
Author Response File: Author Response.docx
Reviewer 2 Report
Dear Author,
The revised draft has been improved. I also approve of the author's reply to my comments.
Yuhai Yang
Author Response
no comments necessary
